Zircon Petrochronology of the Kişladaǧ Porphyry Au Deposit (Turkey)

2021 ◽  
Author(s):  
Luca Paolillo ◽  
Massimo Chiaradia ◽  
Alexey Ulianov
Keyword(s):  
Wall Rock ◽  
Western Anatolia ◽  
Deposit Formation ◽  
Porphyry Deposit ◽  
Porphyry Deposits ◽  
High K ◽  
Magmatic Processes ◽  
Back Arc ◽  
Tectonic Environments

Abstract Porphyry deposits typically occur in subduction-related arcs but have more recently also been described in postsubduction, collisional to extensional back-arc settings. These different tectonic environments not only might imply different genetic processes but also seem to result in different metal endowments (e.g., Au rich versus Cu rich). It is therefore relevant, also for exploration purposes, to understand the magmatic processes involved in porphyry formation in these different tectonic environments. This study focuses on the Kişladaǧ porphyry Au (17.4 Moz) deposit in western Anatolia, which is centered on a series of porphyritic monzonite stocks of high-K calc-alkaline to shoshonitic affinity and formed in a continental rifting environment. With 17.4 Moz of Au, Kişladaǧ is of global metallogenic importance and hence a good example for studying the genetic processes associated with porphyry deposits in extensional back-arc settings. We herein combine a comprehensive set of new zircon textural observations, in situ zircon trace element and Hf isotope data, and previously published zircon geochronology to study the magmatic processes associated with porphyry deposit formation at Kişladaǧ. We show that mafic rejuvenation of a slowly crystallizing (between ~15.8 and 14.9 Ma) magma reservoir below Kişladaǧ immediately preceded porphyry deposit formation. Zircon trace elements and geochronology suggest a longer and deeper evolution for the early fertile magmas compared to the later infertile magmas. Magma evolution at Kişladaǧ was accompanied by crustal wall-rock assimilation. Whole-rock Nd and Sr radiogenic isotopes show that increasing asthenosphere-derived melt input under accelerated regional extension caused a loss in fertility of the system over time.

scholarly journals In Situ Geochemical Compositions of the Minerals in Basaltic Rocks from the West Philippine Basin: Constraints on Source Lithology and Magmatic Processes

Lithosphere ◽  
2020 ◽  
Vol 2020 (1) ◽  
pp. 1-24
Author(s):  
Long Yuan ◽  
Quanshu Yan ◽  
Yanguang Liu ◽  
Shiying Wu ◽  
Ruirui Wang ◽  
...  
Keyword(s):  
Mantle Plume ◽  
Spreading Center ◽  
Minor Amount ◽  
The West ◽  
Basaltic Rocks ◽  
West Philippine Basin ◽  
Geological Evolution ◽  
Magmatic Processes ◽  
Back Arc

Abstract Since the early Cenozoic, the West Philippine Basin (WPB) and the whole Philippine Sea Plate (PSP) has undergone a complex geological evolution. In this study, we presented K-Ar ages, in situ trace element, and major element compositions of minerals of basalts collected from the Benham Rise and the Central Basin Fault (CBF) in the WPB, to constrain their magmatic process and regional geological evolution. Olivine phenocrysts and microlites in the alkali basalts (20.9 Ma) from the Benham Rise have forsterite (Fo) contents of 56.90%–76.10% and 53.13%-66.41%, respectively. The clinopyroxenes in the tholeiites (29.1 Ma) from the CBF is predominantly diopside and augite, and it is depleted in light rare earth elements (LREEs) (LaN/YbN=0.13–3.40) and large-ion lithophile elements (LILEs). The plagioclases in the basalts from both of the Benham Rise and the CBF are predominantly labradorite and andesine, with a minor amount of bytownite, and it is enriched in LREEs, Ba, Sr, and Pb and exhibits strong positive Eu anomalies. However, there exist obvious differences in plagioclase compositions between these two tectonic sites. The source lithology of the Benham Rise basaltic rocks could be garnet pyroxenite, and yet that of the CBF could be spinel-lherzolite. The calculated mantle potential temperature beneath the Benham Rise is 1439°C–1473°C, which is significantly higher than that beneath the CBF (1345°C–1381°C), suggesting there existed thermal anomaly beneath the Rise during basaltic magmatism. This study also calculated the temperature and pressure of the clinopyroxenes and plagioclases, which have been used to indicate magmatic processes. Finally, we suggest that the Benham Rise basaltic rocks may be related to a mantle plume (e.g., the Oki-Daito mantle plume), and the CBF was once located in a back-arc spreading center behind an active subduction zone. The extinction of the Oki-Daito mantle plume activity might be at about 20.9 Ma, and cessation of the back-arc spreading of WPB was at about 29.1 Ma or younger.

Comment and Reply on "Nd isotopic gradients in upper crustal magma chambers: Evidence for in situ magma-wall-rock interaction"

Geology ◽  
1991 ◽  
Vol 19 (2) ◽  
pp. 185
Author(s):  
Benjamin C. Schuraytz ◽  
Thomas A. Vogel ◽  
Leland W. Younker ◽  
G. Lang Farmer ◽  
Kathryn J. Tegtmeyer
Keyword(s):  
Wall Rock ◽  
Magma Chambers ◽  
Rock Interaction ◽  
Crustal Magma

Wide band frequency and in situ characterisation of high permittivity insulators (High-K) for H.F. integrated passives

2006 ◽  
Vol 83 (11-12) ◽  
pp. 2184-2188 ◽  
Author(s):  
T. Lacrevaz ◽  
B. Fléchet ◽  
A. Farcy ◽  
J. Torres ◽  
M. Gros-Jean ◽  
...  
Keyword(s):  
Wide Band ◽  
High Permittivity ◽  
Band Frequency ◽  
Integrated Passives ◽  
High K

Chapter 23: Alteration, Mineralization, and Age Relationships at the Kışladağ Porphyry Gold Deposit, Turkey

2020 ◽  
pp. 467-495
Author(s):  
T. Baker ◽  
S. Mckinley ◽  
S. Juras ◽  
Y. Oztas ◽  
J. Hunt ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
White Mica ◽  
Western Anatolia ◽  
Low Grade ◽  
Porphyry Deposits ◽  
Magmatic Arc ◽  
Argillic Alteration ◽  
Metamorphic Basement ◽  
Slab Tear ◽  
Roll Back

Abstract The Miocene Kışladağ deposit (~17 Moz), located in western Anatolia, Turkey, is one of the few global examples of Au-only porphyry deposits. It occurs within the West Tethyan magmatic belt that can be divided into Cretaceous, Cu-dominant, subduction-related magmatic arc systems and the more widespread Au-rich Cenozoic magmatic belts. In western Anatolia, Miocene magmatism was postcollisional and was focused in extension-related volcanosedimentary basins that formed in response to slab roll back and a major north-south slab tear. Kışladağ formed within multiple monzonite porphyry stocks and dikes at the contact between Menderes massif metamorphic basement and volcanic rocks of the Beydağı stratovolcano in the Uşak-Güre basin. The mineralized magmatic-hydrothermal system formed rapidly (<400 kyr) between ~14.75 and 14.36 Ma in a shallow (<1 km) volcanic environment. Volcanism continued to at least 14.26 ± 0.09 Ma based on new age data from a latite lava flow at nearby Emiril Tepe. Intrusions 1 and 2 were the earliest (14.73 ± 0.05 and 14.76 ± 0.01 Ma, respectively) and best mineralized phases (average median grades of 0.64 and 0.51 g/t Au, respectively), whereas younger intrusions host progressively less Au (Intrusion 2A: 14.60 ± 0.06 Ma and 0.41 g/t Au; Intrusion 2 NW: 14.45 ± 0.08 Ma and 0.41 g/t Au; Intrusion 3: 14.39 ± 0.06 and 14.36 ± 0.13 Ma and 0.19 g/t Au). A new molybdenite age of 14.60 ± 0.07 Ma is within uncertainty of the previously published molybdenite age (14.49 ± 0.06 Ma), and supports field observations that the bulk of the mineralization formed prior to the emplacement of Intrusion 3. Intrusions 1 and 2 are altered to potassic (biotite-K-feldspar-quartz ± magnetite) and younger but deeper sodic-calcic (feldspar-amphibole-magnetite ± quartz ± carbonate) assemblages, both typically pervasive with disseminated to veinlet-hosted pyrite ± chalcopyrite ± molybdenite and localized quartz-feldspar stockwork veinlets and sodic-calcic breccias. Tourmaline-white mica-quartz-pyrite alteration surrounds the potassic core both within the intrusions and outboard in the volcanic rocks. Tourmaline was most strongly developed on the inner margins of the tourmaline-white mica zone, particularly along the Intrusion 1 volcanic contact where it formed breccias and veins, including Maricunga-style veinlets. Field relationships show that the early magmatic-hydrothermal events were cut by Intrusion 2A, which was then overprinted by Au-bearing argillic (kaolinite-pyrite ± quartz) alteration, followed by Intrusion 3 and late-stage, low-grade to barren argillic and advanced argillic alteration (quartz-pyrite ± alunite ± dickite ± pyrophyllite). Gold deportment changes with each successive hydrothermal event. The early potassic and sodic-calcic alteration controls much of the original Au distribution, with the Au dominantly deposited with feldspar and lesser quartz and pyrite. Tourmaline-white mica and argillic alteration events overprinted and altered the early Au-bearing feldspathic alteration and introduced additional Au that was dominantly associated with pyrite. Analogous Au-only deposits such as Maricunga, Chile, La Colosa, Colombia, and Biely Vrch, Slovakia, are characterized by similar alteration styles and Au deportment. The deportment of Au in these Au-only porphyry deposits differs markedly from that in Au-rich porphyry Cu deposits where Au is typically associated with Cu sulfides.

scholarly journals Differentiating between Inherited and Autocrystic Zircon in Granitoids

2020 ◽  
Vol 61 (8) ◽  
Author(s):  
Hugo K H Olierook ◽  
Christopher L Kirkland ◽  
Kristoffer Szilas ◽  
Julie A Hollis ◽  
Nicholas J Gardiner ◽  
...  
Keyword(s):  
Trace Element ◽  
Source Region ◽  
Wall Rock ◽  
Magma Source ◽  
Trace Element Data ◽  
Element Data ◽  
Age Constraints ◽  
Erroneous Interpretation ◽  
Zircon Fraction

Abstract Inherited zircon, crystals that did not form in situ from their host magma but were incorporated from either the source region or assimilated from the wall-rock, is common but can be difficult to identify. Age, chemical and/or textural dissimilarity to the youngest zircon fraction are the primary mechanisms of distinguishing such grains. However, in Zr-undersaturated magmas, the entire zircon population may be inherited and, if not identifiable via textural constraints, can lead to erroneous interpretation of magmatic crystallization age and magma source. Here, we present detailed field mapping of cross-cutting relationships, whole-rock geochemistry and zircon textural, U–Pb and trace element data for trondhjemite, granodiorite and granite from two localities in a complex Archean gneiss terrane in SW Greenland, which reveal cryptic zircon inheritance. Zircon textural, U–Pb and trace element data demonstrate that, in both localities, trondhjemite is the oldest rock (3011 ± 5 Ma, 2σ), which is intruded by granodiorite (2978 ± 4 Ma, 2σ). However, granite intrusions, constrained by cross-cutting relationships as the youngest component, contain only inherited zircon derived from trondhjemite and granodiorite based on ages and trace element concentrations. Without age constraints on the older two lithologies, it would be tempting to consider the youngest zircon fraction as recording crystallization of the granite but this would be erroneous. Furthermore, whole-rock geochemistry indicates that the granite contains only 6 µg g–1 Zr, extremely low for a granitoid with ∼77 wt% SiO2. Such low Zr concentration explains the lack of autocrystic zircon in the granite. We expand on a differentiation tool that uses Th/U ratios in zircon versus that in the whole-rock to aid in the identification of inherited zircon. This work emphasizes the need for field observations, geochemistry, grain characterization, and precise geochronology to accurately determine igneous crystallization ages and differentiate between inherited and autocrystic zircon.

Geochemistry of axial lavas from the mid- and southern Mariana Trough, and implications for back-arc magmatic processes

2019 ◽  
Vol 113 (6) ◽  
pp. 803-820
Author(s):  
Quanshu Yan ◽  
Pingyang Zhang ◽  
Ian Metcalfe ◽  
Yanguang Liu ◽  
Shiying Wu ◽  
...  
Keyword(s):  
Magmatic Processes ◽  
Back Arc

In Situ Stress Measurement and Surrounding Rock Stability Analysis of the Gaoligong Mountain Tunnel

2014 ◽  
Vol 501-504 ◽  
pp. 1766-1773
Author(s):  
Lin Hai Bao
Keyword(s):  
Large Deformation ◽  
Principal Stress ◽  
Stress Measurement ◽  
Pressure Coefficient ◽  
Horizontal Stress ◽  
Wall Rock ◽  
In Situ Stress ◽  
Rock Stability ◽  
Mountain Tunnel

Gaoligong Mountain tunnel is the key project in the Dali-Ruili Railway. In order to optimize the design and guide construction, In-situ stress has been conducted in five boreholes using hydraulic fracturing method, the current shallow crustal in-situ stress state at the project area are obtained according to the measurements results, and deep in-situ stress is predicted using lateral pressure coefficient. The test results show that at depths ranging from 299-979m, the maximum horizontal principal stress is 5.33-30.12Mpa, the minimum horizontal principal stress is 4.94-23.11Mpa, the horizontal principal stress reach 30Mpa at maximum the depth of burial, indicating that the engineering stress filed is dominated by horizontal stress. Based on the In-situ stress data and different distinguish methods, rockburst and large deformation are predicted. The results show that In-situ stress magnitude in this area is classified as high level, and the direction of the maximum horizontal stress is NEE, In-situ stress orientation is conductive to stable of the tunnel. When the tunnel passes through the deep-burial and hard rock, the wall rock may happen rockburst; and the large deformation may happen when the tunnel pass through the weak rock. In order to avoid the disadvantage conditions, reasonable excavation method and safety support method should be adopted during tunnel excavating.

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